<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>css使用规范</title>

  <style>
    h1 {
      color: aqua;
      font-size: medium;
    }
  
    </style>
</head>

<body>
  <h1>
    今天天气不错
  </h1>
</body>
</html>